U.S. Pat. No. 2,559,227 (Rieber) describes a high frequency shock wave generator apparatus comprising a reflector 80 in the form of a truncated ellipsoid suitable for reflecting shock waves, said reflector comprising a cavity 80A constituting a reflection chamber for said shock waves and having the same truncated ellipsoidal shape, with one of the two focuses of the ellipsoid being disposed inside the chamber at its nontruncated end, and with said chamber being filled with a shock wave transmitting liquid 83, e.g. an oil. This apparatus also includes a shock wave generator device which is generally constituted by two electrodes 12 and 13 and which is at least partially disposed inside the chamber 80A, having the two electrodes disposed to generate an electric arc or discharge at the focus which is situated inside the chamber away from the truncated portion of the ellipsoid, and with means 10 and 11 being provided to selectively deliver an instantaneous electrical voltage to the electrodes 12 and 13, thereby giving rise to an electric arc or discharge between the electrodes and thus generating shock waves in the liquid contained in the chamber (see FIG. 3 and column 7, line 51 to column 9, line 30).
The electrodes 12 and 13 are made of a highly conductive material such as copper or brass and they are mounted on an insulator 26 which is pivotally supported by means of a device 11a, 11b for adjusting the spacing therebetween (see column 4 lines 42 to 53 and column 8, lines 41 to 47).
Patent document U.S. Pat. No. 3,942,531 also describes a similar apparatus in which the liquid is constituted by water (see page 3, lines 23 to 24).
When employing a Rieber apparatus or a similar apparatus, it has been observed that a discharge at the electrodes is accompanied by metal being torn away therefrom, thus wearing the electrodes in a manner which is a function of the discharge current that sets up a plasma between the electrodes and generates a sudden pressure wave. The electrodes wear relatively quickly, for example using electrodes having a diameter of 2 mm and made of Z 80 steel, the speed of wear is 1 mm per 800 discharges, and this constitutes a major drawback which greatly increases the cost of using the apparatus.
Proposals have already been made in U.S. Pat. No. 4,608,983 to provide an electrode-advancing device 36, 38 (FIG. 3) including a control member 48 which controls simultaneous advance or retraction movement of the electrodes by being rotated in one direction or the other (see page 9, line 11 to page 10, line 11).
Implementing the structure for supporting and advancing the electrodes is relatively complicated and high in price.
Proposals have also been made in U.S. Pat. No. 4,730,614 concerning devices for advancing electrodes which are much simpler to implement, and which provide greater accuracy in advancing the electrodes.
However, none of these prior apparatuses makes it possible to detect the amount of electrode wear with a high degree of accuracy.
Further, none of these prior apparatuses makes it possible to detect and correct the position of the electrodes at any moment.
Said method and apparatus recently proposed by the Applicants provide entire satisfaction.
However, for industrial applications, it is necessary to simplify the method of detecting and correcting the position of the electrodes, and to provide a device which is easy to implement, which is cheap, and which is highly reliable.
Further, when the prior device is permanently mounted on the ellipsoidal reflector, as is desirable, the vibrations emitted during discharges may damage the device. Also, the differences in light intensity between two different bulbs require the system to be recalibrated. Shock waves which are repeated thousands of times may damage the protective glass, and deposits may occur on the glass, thereby changing the setting of the detector device which is generally of the CCD type.
Preferred implementations of the present invention therefore solve a new technical problem of enabling the position of each of the electrodes to be detected with high accuracy or precision in order to enable the positions of the electrodes to be corrected at any moment with high accuracy or precision; this solution should be of a particularly simple design, highly practical to implement at low cost, and very reliable for use in an industrial application.
Preferred implementations of the present invention also seek to provide a method and apparatus for detecting and correcting the position of electrodes applicable to all types of electrode-using apparatuses, but preferably particularly suitable for use in shock wave generator apparatuses, and also preferably in such apparatuses which include a shock wave generator device including a truncated ellipsoidal reflector.
These technical problems are solved for the first time by the present invention in a satisfactory manner.